Electric welding apparatus



May 20, l941- R. M. WHITE 2,242,691

ELECTRIC WELDING APARTUS Filed lay 9, 1938 2 Sheets-Sheet 1 in 7l I l 21M@ llllllillllllll/l/ g wvwwkw 7U @Oy/1f. wma?, x

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May 20, 1941. R M wHlTE 2,242,691

ELECTRIC WELDING APPARATUS Filed lay 9, 1938 2 Sheets-Sheet 2 Patented May 20, 1941 UNITED STATES PATENT GFFICE mcwimmss lornwhltesnthhnsenacaur.

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The present invention relates to automatic electric welding apparatus. Although not conlined to such work, the invention is particularly adapted for welding small stainless steel members of dental assemblies, in the initial manufacturingofsuchdevicesandintherepairofbroken parts upon the work and the duration of the welding` current for each weld. As a consequeme, many faulty weids were made. particularly when working on light, delicate parts, by reason of the ap-I piication of an incorrect pressure to the work between the electrodes. or by reason of too long or too short a period of time of welding current ilow. 4

It will be understood that in welding stainless steel parts of dental assemblies, there is a definite relation between the value of the welding current, the pressure applied to the work and the duration of the welding current. If the steel is heated to excess, its temper is destroyed, and, since stainless steel is tempered by cold rolling, the lost temper cannot be restored by any heat treatment. In order to prevent undue heating of the parts and a consequent destruction of the temper, it is desirable to apply a relatively heavy welding current to the work fm' a very short time. However, the duration of the current now, although of extremely short time, must be accurately determined. To this end, the invention contemplates an adjustable timer for electric welding currents, characterised by extreme accuracy, whereby minute time adjustments may be exactly determined and effected. Y

'Ihe invention also contemplates adjustable means for accurately determining the pressure applied to the work, thereby eliminating the human factor in this phase of the operation.

The invention further contemplates a new method of welding metals which are not highly resistant to the of electric current. In welding gold and gold alloys of low resistance. the method comprises inserting the gold parts between plates oi relatively highLv resistant metal such as stainless steel. When the welding current is passed through the assembly, the plates of resistant heated suillciently to transmit a welding to the gold parts. thereby securing them together.

In the a drawings, a specific embodiment of the invention is disclosed, but it must be understood that the invention is not limited to the details oi' construction disclosed therein and described below.

In the accompanying drawings:

Figure l is a vertical section, partly in elevation, showing the timer for the welding current and the pressure applying means for the electrodes.

Figure 2 is an end elevation, partly in section, of the apparatus shown in Figure 1.

Figiue 3 is a horizontal section taken on line 3 3 of Figure 1, and

Figure 4 is a circuit diagram.

In the drawings, a transformer casing III supports. on its side, a mercury drip timer represented generally at Il. The top of the transformer casing supports the welding electrode assembly I2. The transformer il (Fig. 4) is disposed interiorly of the casing It. Current from the lines LI, L2 is conducted through a conventional switch Il and through the timer Il to the primary side oi.' the transformer I l. Lines Il, Il lead respectively to the upper electrode il and the lower electrode It. As a result of the inter-position of the timer I I in theprimary circuit oi' the transformer, the welding current may be accurately controlled thereby. The timer comprises an upper casing or distributor block 2l which may have its upper end formed to provide a reservoir 2l, for a quantity oi! mercury or current conducting liquid 22. The reservoir has a downwardly opening passage 23 communieating with a central, horizontally disposed, cylindrical bore 24. In the bore, there is disposed a cylindrical block 25, similar to the body of a plug valve. The block is provided with a piurality of measuring receptacles 2t, 28', 21, 21', 2l, 28', each extending from its periphery to a central bore 28. Each receptacle is provided with a reduced neck 29 at its inner end which is in communication with the aforesaid central bore. Ihe receptacles are preferably arranged in sets of two or more, each member of a set being of the same size, but the receptacles of the different sets being of diil'erent volumes.

The casing 2l, at its lower side, is provided with a downwardly facing opening It, aligned with the passage 2l. The opening 30 communicates with a discharge conduit 3l, preferably threaded in an appropriate bore in the casing 20.

`A pair of spaced contact elements I2, Il are associated with the conduit 3l, in position to be electrically connected by a body of current conducting liquid fiowing downwardly under the inlfiuence of gravity through the conduit 3|. The contact 32 may be connected by a binding post 34 with the main current line L2. The other contact is similarly connected at 35 by a line 35' to the transformer. Thus, when the contacts are electrically connected by a body of mercury or the like, the transformer will be energized and a welding current will ilow to the welding electrodes.

As a means for varying the duration of time during which the contacts are so interconnected, the spacing of the contacts may be varied, or the volume of the body of mercury deposited into the conduit 3| may be varied, or both o1' these variable factors may be employed. Preferably, the space between the contacts may be changed by shifting their relative positions longitudinally, laterally, or rotationally. Any suitable construction i'or this purpose may be employed and the one shown in the accompanying drawings is illustrative only. A stationary block 36 is secured to the side face of the transformer block by screws 31 or the like. The block has a vertically disposed bore 33, in which a tubular sleeve 33 is slidably mounted. 'I'he sleeve is slotted at 40, to accommodate the fixed, upper contact element 32 which is mounted in the block 36 and projects through a wall of the conduit 3|.

A lower bracket 4| is slidably mounted i'or verticalfmovement in ways 42 associated with a lower extension 43 oi' the stationary block. The sleeve 39 is securedv in the bore 44 of the movable bracket 4| by set screws 45 or the like. An upwardly extending portion of the bracket 4| carries the lower contact element 33 and the latter projects through a slot 46 in the conduit 3|. A lug 41, projecting laterally from the movable bracket, is provided with a threaded bore receiving a threaded shaft 43 attached to an adjusting nut 49 rotatably mounted in a lug 53 projecting forwardly from the lower portion 43 of the xed bracket. A pointer 5| associated with the movable bracket registers with a gauge 52 adjacent thereto, so that the space between the contact elements may be accurately determined and adjusted by means of the adjusting screw 43.

Means are provided to facilitate the discharge of mercury or the like from the receptacles associated with the cylindrical block 25. A pipe 60 projects axially into the central bore 23* of the block 25. The pipe has a closed end and a downwardly facing discharge aperture 6|, aligned with the opening 30 in the casing 23. The pipe 60 is connected at its other end through a valve 62 with a conduit 63, leading from a source of air under pressure.

The position of the cylindrical block 25 is determined by a spring-pressed ball 65 mounted in a bore in the upper casing. The ball rides in peripheral grooves 66 and seats in spherical recesses 61. By manipulating the handle 63, the cylindrical block 25 may be moved longitudinally until the ball seats in one of the grooves 66. whereupon the corresponding receptacles will be in the vertical plane of the passage 23 and the discharge opening 30. If the handle is rotated until the ball 65 is projected into one oi' the recesses 61, the operator will be advised of the fact that one receptacle is directly beneath the passage 23 in position to recel/ye a charge oi' mercury from the reservoir. /I/f the handle 63 and the cylindrical block 25 are now rotated through the filled cup will be positioned between the opening 6| in the air pipe 60 and the opening 33 communicating with discharge conduit 33, whereupon the mercury will be emptied into the conduit, its ilow being facilitated by air admitted into the inverted, bottom end oi the measuring cup. The individual cups of a set may be4 disposed 180 apart, o'r any other desired relation may be employed. Moreover, instead of employing the reservoir 2|, a simple funnel oi' smaller capacity may be used to guide abody of mercury into each cup.

When the mercury is emptied into the conduit 3|, it flows downwardly therethrough under the influence of gravity and eventually is co1- lected in a receptacle 10. During its passage through the conduit, it bridges the space between the contact elements 32, 33, thereby completing the primary circuit of the transformer and initiating a iiow of welding current to and through the electrodes |1, i3. The duration oi' time that the contact elements are so connected depends upon two principal factors, i. e.. the spacing of the electrodes and the volume of the body of mercury. If the space between the contacts is increased, obviously it will take a. longer time for the mercury to reach the lower element after contacting the upper one, and the mercury will break away from the upper contact more quickly thereafter, whereby the duration of circuit completion is reduced. On the other hand, ii' the contacts are moved closer together, they will remain connected in the electric circuit for a relatively longer period of time by the downwardly moving body of mermuy.

If the-volume of the body of mercury is increased, for instance, by using one of the measuring cups 21 or 21', it will take longer for that body to pass the two electrodes and an increase in the time of the welding current will result. On the contrary, if a smaller measuring cup 23 is used, the time of inter-connection of the contact elements will'be reduced.

It should be understood that minute periods of time are being dealt with and extreme accuracy of time control is of paramount importance. The apparatus disclosed herein effects the desired accurate control of currents of minute duration with remarkable emciency.

Any preferred means may be employed for applying a constant, predetermined, adjustable pressure to the work between the electrodes, and it must be understood that the arrangement shown in the accompanying drawings is illustrative only.

The lower electrode |3 is secured in adjustable, fixed position in a chuck 1| projecting upwardly from the transformer blocks I0. The welding current is conducted to that electrode through the wire I6 and the parts are appropriately insulated from the frame of the ma.- chine. A post 12 projects upwardly from the frame in spaced relation to the lower electrode and, by means oi' an adjustable set screw 13 or the like, one piece of the work 14 may be secured in place. The second piece of work 15, which is to be welded to the iirst, may be positioned between the lower electrode I3 and the iirst piece, and be held temporarily in place by the resilient pressure of the first piece as clamped on the post 12.

The means for applying predetermined pressure to the upper electrode |1 comprises an upwardly and laterally projecting arm 16 having,

at its free end, a-spring seat il, surrounding a verticalbore'llinwhichthepost'llcarrying the electrode il is slidably mounted. The electrode I1 issecuredtothepost 'Il byanapproprlately insulated chuck Il to which the wire Ili'isiattached. v

Upon the upper surface oi' the xed arm 1l, there is a nrst lever 8| iulcrumed on a bracket l! and provided with a rearward extension It. The lever adjacent its forward end carries an imstanding fulcrum bracket I4 for a second lever il, pivoted thereto at It. The forward end oi the lever Il is pivoted at Il to a downwardly hanging yoke It, carrying. at its lower end, an annular spring seat Il, surrounding the electrode carrying post 'Il and slidable with respect thereto. A coiled compression spring Il is interposed between the annular spring seat Il carried by the yoke and the lower tace oi' the spring seat 11 on theend oi the stationary arm. A second, lighter coil spring 02 is disposed between the upper face oi the seat 11 and the free end Il oi the nrst lever Il. 'Ihat end of the lever projects through a slot I4 formed in the upper end oi the electrode supporting post 1l.

Adjacent its rear end Il. the second lever il carries an adjustable link II which may be secured to the rear extension I3 oi the first lever Il in a plurality of diilerent positions, to vary the force applied to the upper electrode I1.

In-the operation of the clamping means, when the work has been positioned above the lower ior guiding the measured drops oi lliquid along apathpastsaidcontacts, andmeansforvarying the duration of time in their moments that said dwp! bridge the space betwecnsaid contac electrode I8, the handle Il o! the lever II is` moved downwardly, thereby depressing the free end Il of the lever li and collapsing the spring l2, which,- as stated above, is considerably weaker than the spring el. When the upper electrode II contacts the work, its further down: ward movement will be arrested, as well as the further downward movement oi' the end It of the lever Il. As the handle Il oi' the other lever `is depressed further, the yoke Il will be raised and the spring Il compressed a predetermined amount. 'Ihe degree of compression of the spring I. determines the amount of pressure applied to the work, through the yoke Il, lever Il, bracket Il, and the free end Il of lever 8|.

'I'he force applied by the upper electrode to the work also may be varied by changing the positions of the fulcrums oi the levers or by changing the strength of the spring 9|. The particular advantage oi' the construction disclosed is that when the parts have once been determined and adjusted with accuracy, the same force will be applied to all pieces of work placed between i the electrodes, thereby eliminating the human element applying iorce to the work.

It will be understood that the primary function of the spring l2 is simply to raise the parts to an upwardly disposed inoperative position, thereby providing a spaceof substantial height between the lower and upper electrodes to facilitate positioning the work on the lower electrodes.

As stated above, the invention is not limited to the details of construction disclosed in the accompanying drawings, but must be construed to cover all changes and modications coming' within the scope of the appended claims and their equivalents.

I claim:

l. A timer for an electric circuit, comprising means for measuring drops oi current conducting liquid of predetermined volume, a pair of spaced contact elements in said circuit, means elemnts. Y

2. A timer for an electric circuit, comprising means i'or measuring small. separated, independent bodies oi current conducting liquid of predetermined volume, a pair oi spaced contacts, means for successively discharging said bodies ot liquid from the measuring means, means for guiding the discharged bodies of liquid along a path past said contacts. and means for varying the duration oi'time in their movement that said bodies bridge the space and establish electrical communication between said `\contact elements.

3. A timer for an electric circuit, comprising means i'or measuring minute bodies of current conducting liquid of predetermined volume, means for dropping the bodies, as independent units, successively, at spaced intervals oi time from the measuring means to cause ,the measurcd bodies to move under the inuence of gravity along a predetermined path, a pair of contact elements spaced along said path, and means ior vrying the duration of time in their movements that said bodies are in contact with both of said contact elements.

4. A timer i'or an electric circuit.' comprising means for measuring bodies oi' current conducting liquid of predetermined volume, a pair of spaced contact elements, means for guiding the measured bodies of liquid along a path past said contacts, and means for varying the volume of the bodies of liquid measured by said measuring means, thereby to vary the duration oi time that said bodies bridge the space between -said contact elements in their movement along said path.

5. A timer for an electric circuit, comprising means for measuring small, separated, independent bodies oi current conducting liquid of prcdeterminedvolume, a 4pair oi' spaced contact elements, means for guiding the measured bodies o! liquid along a path past said contacts,v

and means for varying the spacing of the con,-y tacts lengthwise in said path, thereby to vary the duration of time during which said separated, independent bodies bridge the space between the contact elements in the movement oi' said bodies along said path.

6. A timer for an electric circuit, comprising a receptacle for measuring a, drop of current conducting liquid of predetermined, minute vol ume, a conduit along which the measured drop may flow from said receptacle, and a pair of spaced contacts associated with said conduit and positioned to be electrically connected by said drop during its passage along said conduit.

7. A timer i'or an electric circuit, comprising a plurality of receptacles of diilerent sizes adapted to measure bodies of current conducting liquid of predetermined, variable volume, a conduit,

means for emptying the contents oi' any of the receptacles into the conduit, a pair o f spaced contact elements associated with the conduit and positioned to be electrically connected by the bodies of liquid flowing along the conduit, the

volume oi each body serving to determine the adapted to receive all of the liquid from said receptacle and to conduct the same as a unitary body under the influence ofgravity, a pair of spaced contacts associated with said conduit and positioned to be electrically connected by said body of liquid during its passage along said conduit, and means for varying the space lengthwise of the conduit between said contacts to vary the duration of time that the body of liquid connects the contacts during its passage along the conduit.

9. A timer for an electric welding circuit, cornprising a vreservoir having a discharge opening in its bottom for a supply of current conducting liquid, a cylindrical block having a measuring cup formed in its periphery registrable with said discharge opening to receive a measured body of liquid, a discharge conduit below said block, said block being rotatable about its axis to empty the contents of the cup into the conduit, and a pair of spaced contacts associated with said conduit and positioned to be electrically connected by said liquid during its passage along the conduit.

10. A timer for an electric welding circuit, comprising means for holding a supply of current conducting liquid, a rotatably mounted measuring cup adapted to be brought into charging relation to said supply, alconduit positioned to receive the contents of the cup discharged upon rotation of the same, means for admitting air to the bottom of the cup in discharging position to facilitate the discharge of the contents therefrom, and a pair of spaced contacts associated with said conduit and positioned to ybe electrically connected by the discharged liquid during its passage along said conduit.

11. A timer for an electric welding circuit, comprising a receptacle for a supply of current conducting liquid having a downwardly opening discharge orifice, a cylindrical block below said opening having a. central bore and a plurality of measuring cups, each extending from the periphery to said bore, said block being mounted for rotation about and for endwise movement along its axis to register any of said cups with said discharge opening, a conduit below said block positioned to receive the contents of a filled cup upon inversion of the same, an air pipe disposed in the bore of said block and having an opening aligned with said conduit to admit air to the bottom oi an inverted cup registering with said conduit, thereby to facilitate the discharge of liquid from the cup to the conduit, and a pair of spaced contacts associated with said conduit and positioned to be electrically' connected by the discharged liquid during its passage along said conduit.

12. A device in accordance with claim 11 characterized in that the measuring cups in the block are of varying volumes, whereby bodies of liquid of predetermined, different volume may be caused to travel along said conduit, thereby varying the length of time that said contacts are electrically connected.

13. A device in accordance with claim 9 characterized by the provision of means for varying the spacing between said contacts, thereby to vary the duration oi time during which the liquid bridges the space between the contacts in the movement of the liquid along the conduit.

14. A timer for an electric welding circuit, comprising a casing having a horizontally disposed cylindrical chamber therein, a funnel having a downwardly opening passage communicating with the chamber, a' discharge conduit in alignment therewith, a compressed air conduit disposed axially in said chamber and having an opening facing the discharge conduit, a. cylindrical block in the chamber having an axial bore telescoped on said air conduit, said block having a plurality of measuring cups extending from its periphery to its central bore and each adapted first to register first with the funnel to be filled with a current conducting liquid therefrom, and then to register with the discharge .conduit and the air conduit opening to facilitate the discharge of liquid into said conduit,.and a pair of spaced contact elements in said conduit adapted to be electrically connected by the quantity of liquid passing therethrough.

15. A timer for an electric circuit comprising a pair of spaced contact elements in said circuit, means for delivering a measured drop of currentconducting liquid, and means for conducting the same along a. path past said contacts.

16. An adjustable timer for an electric circuit comprising a pair of spaced contact elements in said circuit, means for conducting a measured drop of current-conducting liquid along a path past said contacts to establish connection between the contacts and complete the circuit, and means for varying the distance between said contacts, thereby to vary the time that the contacts are so connected by said drop during its movement along said path.

17. An adjustable timer for an electric circuit comprising a pair of spaced contact elements in the circuit, a reservoir for a supply of current conducting liquid, means for separating from said supply a small body of liquid and for accurately measuring the body, and me'ans for conducting the separated, measured body of liquid along a path past said contacts to complete the circuit therebetween.

ROY M. WHITE. 

